Variation in the climatic response to SRES emissions scenarios in integrated assessment models

Integrated assessment models (IAMs) have commonly been used to understand the relationship between the economy, the earth’s climate system and climate impacts. We compare the IPCC simulations of CO₂ concentration, radiative forcing, and global mean temperature changes associated with five SRES ‘marker’ emissions scenarios with the responses of three IAMs—DICE, FUND and PAGE—to these same emission scenarios. We also compare differences in simulated temperature increase resulting from moving from a high to a low emissions scenario. These IAMs offer a range of climate outcomes, some of which are inconsistent with those of IPCC, due to differing treatments of the carbon cycle and of the temperature response to radiative forcing. In particular, in FUND temperatures up until 2100 are relatively similar for the four emissions scenarios, and temperature reductions upon switching to lower emissions scenarios are small. PAGE incorporates strong carbon cycle feedbacks, leading to higher CO₂ concentrations in the twenty-second century than other models. Such IAMs are frequently applied to determine ‘optimal’ climate policy in a cost–benefit approach. Models such as FUND which show smaller temperature responses to reducing emissions than IPCC simulations on comparable timescales will underestimate the benefits of emission reductions and hence the calculated ‘optimal’ level of investment in mitigation.     

Lipid Partitioning in the Hydrothermal Vent Shrimp Rimicaris exoculata

Abstract. This study examines the composition and partitioning of lipids in the alvinocarid shrimp Rimicaris exoculata from Mid-Atlantic hydrothermal vents. Juveniles and adults at different stages of reproductive development were dissected into abdomen, branchial and ovary/hepatopancreas tissues. Each of these tissues was analysed for total lipid and lipid class composition, and fatty acids and fatty alcohols were identified using GC and GC-MS. Adult and juvenile shrimp differ in the partitioning of lipids between tissues. Juveniles store lipids in the abdomen as wax ester droplets and may use phosphatidyl choline as an additional reserve. Adult shrimp use triglycerides as an energy store, and triglycerides and polar lipids accumulate in ovary and hepatopancreas tissue during reproductive development. The wax ester storage droplets of juvenile shrimp contain high concentrations of n-3 fatty acids, which are photosynthetically-derived and thought to be important for reproductive development in crustaceans. These n-3 fatty acids are concentrated in the ovary and hepatopancreas of adults compared to other tissues. The n-3 fatty acid content of these adult tissues is well within that estimated for whole juvenile shrimp, supporting the hypothesis that the n-3 fatty acids putatively required for adult reproduction are stored from the juvenile stage.     

Burial dolomitization driven by modified seawater and basal aquifer‐sourced brines: Insights from the Middle and Upper Devonian of the Western Canadian Sedimentary Basin

Dolomitization in the Western Canadian Sedimentary Basin has been extensively researched, producing vast geochemical datasets. This provides a unique opportunity to assess the regional sources and flux of dolomitizing fluids on a larger scale than previous studies. A meta‐analysis was conducted on stable isotope, strontium isotope (⁸⁷Sr/⁸⁶Sr), fluid inclusion and lithium‐rich formation water data published over 30 years, with new petrographic, X‐ray diffraction, stable isotope and rare‐earth element (REE+Y) data. The Middle to Upper Devonian Swan Hills Formation, Leduc Formation and Wabamun Group contain replacement dolomite (RD) cross‐cut by stylolites, suggesting replacement dolomitization occurred during shallow burial. Stable isotope, REE+Y and ⁸⁷Sr/⁸⁶Sr data indicate RD formed from Devonian seawater, then recrystallized during burial. Apart from the Wabamun Group of the Peace River Arch (PRA), saddle dolomite cement (SDC) is more δ¹⁸O_(PDB) depleted than RD, and cross‐cuts stylolites, suggesting precipitation during deep burial. SDC ⁸⁷Sr/⁸⁶Sr data indicate contributions from ⁸⁷Sr‐rich basinal brines in the West Shale Basin (WSB) and PRA, and authigenic quartz/albite suggests basinal brines interacted with underlying clastic aquifers before ascending faults into carbonate strata. The absence of quartz/albite within dolomites of the East Shale Basin (ESB) suggests dolomitizing fluids only interacted with carbonate strata. We conclude that replacement dolomitization resulted from connate Devonian seawater circulating through aquifers and faults during shallow burial. SDC precipitated during deep burial from basinal brines sourced from basal carbonates (ESB) and clastic aquifers (WSB, PRA). Lithium‐rich formation waters suggest basinal brines originated as residual evapo‐concentrated Middle Devonian seawater that interacted with basal aquifers and ascended faults during the Antler and Laramide Orogenies. These results corroborate those of previous studies but are verified by new integrated analysis of multiple datasets. New insights emphasize the importance of basal aquifers and residual evapo‐concentrated seawater in dolomitization, which is potentially applicable to other regionally dolomitized basins.     

Seismicity and fluid geochemistry at Lassen Volcanic National Park,California: Evidence for two circulation cells in the hydrothermal system

Seismic analysis and geochemical interpretations provide evidence that two separate hydrothermal cells circulate within the greater Lassen hydrothermal system. One cell originates south to SW of Lassen Peak and within the Brokeoff Volcano depression where it forms a reservoir of hot fluid (235–270 °C) that boils to feed steam to the high-temperature fumarolic areas, and has a plume of degassed reservoir liquid that flows southward to emerge at Growler and Morgan Hot Springs. The second cell originates SSE to SE of Lassen Peak and flows southeastward along inferred faults of the Walker Lane belt (WLB) where it forms a reservoir of hot fluid (220–240 °C) that boils beneath Devils Kitchen and Boiling Springs Lake, and has an outflow plume of degassed liquid that boils again beneath Terminal Geyser. Three distinct seismogenic zones (identified as the West, Middle, and East seismic clusters) occur at shallow depths (< 6 km) in Lassen Volcanic National Park, SW to SSE of Lassen Peak and adjacent to areas of high-temperature (≤ 161 °C) fumarolic activity (Sulphur Works, Pilot Pinnacle, Little Hot Springs Valley, and Bumpass Hell) and an area of cold, weak gas emissions (Cold Boiling Lake). The three zones are located within the inferred Rockland caldera in response to interactions between deeply circulating meteoric water and hot brittle rock that overlies residual magma associated with the Lassen Volcanic Center. Earthquake focal mechanisms and stress inversions indicate primarily N–S oriented normal faulting and E–W extension, with some oblique faulting and right lateral shear in the East cluster. The different focal mechanisms as well as spatial and temporal earthquake patterns for the East cluster indicate a greater influence by regional tectonics and inferred faults within the WLB. A fourth, deeper (5–10 km) seismogenic zone (the Devils Kitchen seismic cluster) occurs SE of the East cluster and trends NNW from Sifford Mountain toward the Devils Kitchen thermal area where fumarolic temperatures are ≤ 123 °C. Lassen fumaroles discharge geothermal gases that indicate mixing between a N₂-rich, arc-type component and gases derived from air-saturated meteoric recharge water. Most gases have relatively weak isotopic indicators of upper mantle or volcanic components, except for gas from Sulphur Works where δ¹³C–CO₂, δ³⁴S–H₂S, and δ¹⁵N–N₂ values indicate a contribution from the mantle and a subducted sediment source in an arc volcanic setting.     

Timing and duration of hydrological transitions in Arctic polygonal ground from stable isotopes

Land surface models and Earth system models that include Arctic landscapes must capture the abrupt hydrological transitions that occur during the annual thaw and deepening of the active layer. In this work, stable water isotopes (δ²H and δ¹⁸O) are used to appraise hydrologically significant transitions during annual landscape thaw at the Barrow Environmental Observatory (Utqiaġvik, Alaska). These hydrologically significant periods are then linked to annual shifts in the landscape energy balance, deduced from meteorological data and described by the microclimatic periods: Winter, Pre-Melt, Melt, Post-Melt, Summer, and Freeze-Up. The tight coupling of the microclimatic periods with the hydrological transitions supports the use of microclimatic periods as a means of linking polygonal surface water hydrology to meteorological datasets, which provides a mechanism for improving the representation of polygonal surface water hydrology in process-based models. Rayleigh process reconstruction of the isotopic changes revealed that 19% of winter precipitation was lost to sublimation prior to melting and that 23% of surface water was lost to evaporation during the first 10 days post-melt. This agrees with evaporation rates reported in a separate study using an eddy covariance flux tower located nearby. An additional 17% was lost to evaporation during the next 33 days. Stable water isotopes are also used to identify the dominant sources of surface water to various hydrogeomorphological features prevalent in polygonal terrain (a lake, a low centre polygon centre, troughs within the rims of low centre polygons, flat centre polygon troughs, a high centre polygon trough, and drainages). Hydrogeomorphologies that retained significant old water or acted as snow drifts are isotopically distinct during the Melt Period and therefore are easily distinguished. Biogeochemical changes related to the annual thaw are also reported and coupled to the hydrological transitions, which provides insight into the sources and sinks of these ions to and from the landscape.     

Investigation of iron sulfide impact crater residues: A combined analysis by scanning and transmission electron microscopy

Abstract– Samples returned from comet 81P/Wild 2 by the Stardust mission provided an unequaled opportunity to compare previously available extraterrestrial samples against those from a known comet. Iron sulfides are a major constituent of cometary grains commonly identified within cometary interplanetary dust particles (IDPs) and Wild 2 samples. Chemical analyses indicate Wild 2 sulfides are fundamentally different from those in IDPs. However, as Wild 2 dust was collected via impact into capture media at approximately 6.1 km s^?1, it is unclear whether this is due to variation in preaccretional/parent body processes experienced by these materials or due to heating and alteration during collection. We investigated alteration in pyrrhotite and pentlandite impacted into Stardust flight spare Al foils under encounter conditions by comparing scanning and transmission electron microscope (SEM, TEM) analyses of preimpact and postimpact samples and calculating estimates of various impact parameters. SEM is the primary method of analysis during initial in situ examination of Stardust foils, and therefore, we also sought to evaluate the data obtained by SEM using insights provided by TEM. We find iron sulfides experience heating, melting, separation, and loss of S, and mixing with molten Al. These results are consistent with estimated peak pressures and temperatures experienced (approximately 85 GPa, approximately 2600 K) and relative melting temperatures. Unambiguous identification of preserved iron sulfides may be possible by TEM through the location of Al‐free regions. In most cases, the Ni:Fe ratio is preserved in both SEM and TEM analyses and may therefore also be used to predict original chemistry and estimate mineralogy.     

Simulations of accidental coal immersion

Coal is currently becoming an increasingly interesting fossil energy resource and that is the reason why its maritime transport, and hence the risk of collier accidents, increase. In this work, the environmental impact of an accidental coal immersion at sea is studied: the physicochemical effects are estimated using innovative experimental setups – a laboratory seawater canal called “polludrome” is used to evaluate the behaviour of coal particles submitted to a seawater flow, and a specifically designed tub is used to study the physicochemical consequences induced when coal is introduced into continuously renewed seawater. When coal is introduced into seawater, the most easily visible consequences are physical: fine coal particles reduce the daylight penetration up to 100% and move along with the flow, and coal chunks accumulate on the floor. Chemical effects are also measured: humic matters are dissolved from coal into seawater (up to 2 mg L⁻¹), but no release of polycyclic aromatic hydrocarbons is evidenced. Some inorganic compounds are dissolved, among which manganese, whose concentrations can reach 1 μg L⁻¹. Fortunately, the results show that the environmental impact of this type of accident would remain limited.     

Infrared remote sensing of atmospheric composition and air quality: Towards operational applications

Atmospheric remote sensing from satellites is an essential component of the observational strategy deployed to monitor atmospheric pollution and changing composition. During this decade, remote sensors using the thermal infrared (TIR) spectral range have demonstrated their ability to sound the troposphere and provide global distribution for some of the key atmospheric species. This article illustrates three operational applications made possible with the IASI instrument onboard the European satellite MetOp, which opens new perspectives for routine observation of the evolution of atmospheric composition from space.